1. Field of the Invention
Embodiments of the present invention generally relate to semiconductor manufacturing and specifically the use of infrared camera for real-time temperature monitoring and control.
2. Description of the Related Art
Virtual Metrology (VM), an increasingly critical component of semiconductor manufacturing control, is a technology to predict metrology variables using information about the state of the process for every substrate. The idea of Virtual Metrology is to construct predictive models that can forecast the electrical and physical metrology variables of substrates, based on data collected from the relevant processing tools, such as temperature, power, flow rate, pressure, optical emission spectrum, plasma impedance, etc. In this way, the time consuming and costly direct measurements of the metrology variables of the substrate can be minimized or eliminated altogether. Virtual Metrology in conjunction with Advanced Process Control (APC) can provide real-time feed-forward control (i.e. to the next process step) and feed-backward control (i.e. to the previous process step) to compensate for disturbance of an upstream process.
High temperature processing systems, such as a rapid thermal processing (RTP) reactor and a chemical vapor deposition (CVD) epitaxial reactor, require a substantially uniform temperature profile across the substrate. In some advanced processes, it is important to have a substantially small temperature gradient from about 2 mm inside the edge of the substrate. Particularly, it may be necessary to heat a substrate to a temperature between about 200° C. to about 1350° C. with a temperature deviation of only about 1° C. to 1.5° C. across the substrate. In such processes, the temperature uniformity may be improved by controlling heat sources, such as a laser and an assembly of lamps that are configured to heat the substrate on the front side while a reflective surface on the back side reflects heat back to the substrate. Furthermore, point temperature measurement and compensation methodology, such as Virtual Metrology and Advanced Process Control, have been used to improve the temperature gradient across the substrate. Examples
Individual temperature sensors, such as pyrometers, have been used to take point measurement of the substrate temperature as input data into the Virtual Metrology and Advanced Process Control system. Conventional processing systems typically use a small number of sensors due to space and cost constraints. To accurately measure the temperature profile of the entire substrate, a prohibitively large number of sensors would be required.
Therefore, there is a need for apparatus and methods to accurately monitor and control in real time the temperature profile across the entire substrate in a processing system.